By St. Gregory Palamas
(From Homily 44)
As Jacob produced twelve patriarchs according to the flesh, from whom the twelve tribes of Israel came into being (Gen. 35:22-26), so spiritually Jesus gave us the twelve initiates into His mystery (Matt. 10:2-4, Mark 3:14-19, Luke 6:13-16, and Acts 1:13). When one of them wretchedly fell away (Matt. 27:5, Acts 1:16-20), the great St. Paul, upon whom Christ had looked down from heaven (cf. Acts 9:3), made up the number.* If we do not see the same number of tribes originating from the apostles, that is nothing at all strange, for spiritual things are divided without losing their unity. In the same way, our body apparently has five senses, but our soul’s perception is single, divided yet united.
The twelve wells of water by which the Israelites, under Moses’ leadership, encamped and quenched their thirst after traveling in the desert foreshadowed these twelve men (Exod. 15:27). For by providing spiritual water they delivered the human race, which had previously been walking through the trackless wastes of unbelief, from the burning heat of mad idolatry. Similarly, the twelve stones which Joshua, son of Nun, set up as a sign in Gilgal after the Israelites had miraculously crossed the Jordan on foot (Josh. 4:9), foreshadowed the twelve apostles, for they are an everlasting sign to us that the true Jesus held back the river of sin that was engulfing the world and allowed those who obeyed Him to pass along life’s path without sin, just as in earlier days He let the Israelites cross the Jordan dry-shod.
But characteristics such as these, and the fact of being called by none other than Christ, the only-begotten Son of God, are common to all the apostles.
Notes:
* Though Acts 1:15-26 tells us that Matthias took the place of Judas as one of the Twelve, this was in fact a formality. Matthias was chosen by lot, but St. Paul was chosen by Christ Himself, and he did not hesitate to call himself an "apostle". This theological understanding of St. Paul being numbered among the Twelve after taking the place of Judas can be observed in Orthodox icons of the Twelve Apostles, where Matthias is usually not depicted though St. Paul is.